Ferrite phase shifter for circularly polarized electromagnetic energy having angularly displaced latching control leads



3,361,993 FERRITE PHASE SHIFTER FOR CIRCULARLY POLARIZED ELECTROMAGNETIC Jan. 2, 1968 R. R. JON ES ETAL ENERGY HAVING ANGULARLY DISPLACED LATCHING CONTROL LEADS Filed Oct. 11, 1965 FIG.|.

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SQUARE LOOP FERR ITE FIG.2.

mfi m w m mm. 5 MR i 8 INC: N F 5 m 1, F f m w Fm Q 4 T: 2 M m S T M ATTOR Y United States Patent 3,361,993 PHASE SHIFTER FUR ClRtZULARLY PGLARHZED ELECTROMAGNETIC ENERGY HAVHNG ANGULARLY DISPLACED LATCH- lZNG CONTROL LEADS Raymond E. Jones, Baltimore, Mtl, and Robert W.

Severance, In, Montgomery, Ala, assignors to Westinghouse Electric Corporation, Pittsburgh, Pa, a corporation of Pennsylvania Filed Get. 11, 1965, Ser. No. 512,836 3 Qlaims. (Cl. 33.3-24.1)

AESCT OF THE DISCLOS The combination of a square loop ferrite centrally disposed within a waveguide and circularly polarized electromagnetic energy propagating therethrough. The circularly polarized wave may be separated into two ortho onal, linearly polarized TE modes each of which react on portions of the ferrite element when magnetized to retard or advance, depending on the state of magnetization, the phase of both modes equally. Latching control leads at the ends of each ferrite element are made to exit at an angle to each other to avoid affecting the operation of the phase shifter. That is, without destroying circularity, coupling out energy, or causing impedance mismatch.

The present invention relates generally to phase shifters for circularly polarized microwave energy and more particularly relates to a latching ferrite phase shifter for selectively retarding and advancing, each by the same amount, the quadrature electric field components present in circularly polarized electromagnetic energy.

Many phased-array radar systems require transmission and reception of circularly polarized RF energy in order to suppress background clutter and for other reasons re lated to the system. A phased-array radar system may transmit on one sense of circular polarization and receive on the other sense. Most systems which operate on circular polarization usually have to transduce the RF energy to linear polarization in order to shift the phase of the RF signal and then return, after phase shift, to circular polarization to transmit or receive.

An object of the present invention is to provide a phase shifter for circularly polarized RF energy which permits phase shift without the necessity of transducing.

An other object of the present invention is to provide a phase shifter which permits digital steering of a phasedarray system.

Briefly, the present invention provides a phase shifter including a ferrite element longitudinally disposed within a waveguide. The ferrite element provides a closed magnetization loop within the waveguide. The two orthogonal, linearly polarized TE modes of the circularly polarized electromagnetic energy each react on those portions of the ferrite element which are transversely magnetized to equally retard or advance the phase of both modes. One state of remanent magnetization within said ferrite element retards the phase of the RF energy and the other mode, advances the RF energy.

Further objects and advantages of the present invention will be readily apparent from the following detailed description taken in conjunction with the drawing in which:

FIG. 1 is a longitudinal sectional view of an illustrative embodiment of the present invention;

FIGS. 2 and 3 are schematic illustrations useful in understanding the operation of the present invention;

FIG. 4 is a cross sectional view taken along the line indicated by the arrows IVIV of FIG. 1;

FIG. 5 is a cross sectional view of another illustrative embodiment of the present invention, and

FIG. 6 is a longtudinal sectional view of still another illustrative embodiment of the present invention.

The phase shifter includes a length of circular waveguide 2 containing a ferrite element 4 with dielectric elements 6 at each end thereof. An aperture 8 longitudinally extends through the ferrite element 4 and dielectric element 6. A latching conductor 10 extends through the aperture and is connected to an external DC. signal source by the latching control wires 12. A dielectric layer 14 permits passage of the latching control wires 12 through the walls of the waveguide 2.

The dielectric elements 6 are chosen to be of quarterwavelengths in size to match the impedance of the empty waveguide to the ferrite loaded guide to minimize reflections. The dielectric elements 6 are chosen to have a dielectric constant (K) of /K -K If the ferrite element 4 is selected to have a dielectric constant of 12 then the dielectric constant of the dielectric elements 6 is chosen to be approximately 4.0. For C-band operation, for example, the dielectric elements 6 have a length of approximately .4 inches.

impinging on the ferrite element 4 is the circularly polarized TE mode. Accordingly, the circularly polarized wave may be separated into two orthogonal, linearly polarized TE modes, each passing through the ferrite element 4.

Each ferrite element 4 is chosen to have a squareloop magnetization in which the remanent magnetization is almost equal to the saturation magnetization. The selected ferrite element 4 is magnetized in a circumferential direction by passing a current therethrough by means of the latching conductor 10. A positive current pulse will magnetize the material to saturation in one direction such as clockwise and the element will retain the larger part of its magnetization when the current pulse is removed. The ferrite element is then said to be latched at its positive remanent magnetization point. However, if a negative current pulse is applied, the magnetization will be reversed and the ferrite element will remain set at its opposite state of remanent magnetization when the current pulse is removed.

FIGS. 2 and 3 illustrate the disposition of the vertical electric field component and the horizontal electric field component, respectively. The magnetic field, h associated with each of the electric field components interacts with the magnetization vectors 2%! and 22, respectively to retard or advance the phase of both electric field components and equal amount. The electromagnetic wave will be advanced or retarded in accordance with the state of magnetization of the ferrite element 4. When it is magnetized in the clockwise direction the wave energy will be retarded, both components by an angle 0 degrees, but the phase quadrature between the vertical and horizontal electrical field components will remain. When the ferrite element 4 is magnetized in the counterclockwise direction to its opposite latched state, thereby assuming the alternate state of remanent magnetization, both electric field components will be advanced by an angle 0 degrees; but both components will remain in quadrature.The phase of circularly polarized mircrowave energy is shifted without the necessity of transducing the energy to linear polarization and then returning, after phase shift, to circular polarization.

From FIG. 4 it can be seen that the latching control wires 12 are not parallel to one another; rather, there is an angle 0t between them. Since the phase shifter operates on a circularly polarized :mode, the latching control leads 12 will be disposed perpendicularly to the longitudinal axis of the guide and therefore cross the magnetic field lines. Energy will be magntically coupled out of the waveguide 2 by means of the latching control wires ii. In order to overcome this loss of energy, the angle or is adjusted in position to cancel the currents induced in the two latching control wires 12 by the RF signal. Since circular polarization is being used, the magnitude of the current induced in both latching control wires 17. is the same regardless of the longitudinal distance between them and therefore only the phase of the current is left to be adjusted. By varying the angle or it is possible to achieve a net cancellation of the induced currents. The angle at which cancellation will be achieved is dependent on the longitudinal distance between the wire ends and the ire quency of the microwave energy through the wave guide 2.

A ferrite element 4 of alternate cross sectional configuration is illustrated in FIG. 5. The toroidal cross section of the element 30 provides the necessary sections of magnetized material for the transverse magnetic field to interact with the field associated with the horizontal and vertical electric field components shown in FIGS. 2 and 3.

FIG. 6 illustrates an n-bit digital phase shifter having a number of ferrite elements, each magnetized by the portion of the latching conductor 10 energized by respective latching control wires 12. The elements may be of varying length in order to meet the particular system requirement for phase shifts of various numbers of degrees.

Operation of the configuration shown in FIGS. 1 and 2, utilizes a 2" length ferrite element containing magnesium manganese ferrite with aluminum substitution and has a /8" x 78" cross section with diameter hole extending longitudinally therethrough. The input circularity was better than 0.1 db, while the output circularity is degraded only to 0.35 db. The input voltage standing ratio was 1.40, at a frequency of 5.8 gc. The angle, a between the control latching wires 12 was approximately 90 mechanical degrees. A figure of merit of 350 per db was measured. In other words, a differential phase shift of 140 was realized and an insertion loss of 0.4 db.

While the present invention has been described with a degree of particularity for the purposes of illustration, it is to be understood that all modifications, alternations and substitutions within the spirit and scope of the present invention are herein meant to be included. For example, while the latching element 4 has been referred to as a ferrite element, it is to be understood that the ele ment may be of any suitable material such as, for example, spinel-type materials and garnet-type ferrites which contain rare earths. It is to be understood that all suitable materials including ferromagnetic materials may be utilized for the latching function necessary for providing the transverse magnetic field and the term ferrite is herein meant to include all such materials.

i We claim as our invention: 1. In combination; a waveguide, means for propagating a circularly polarized radio frequency electromagnetic wave through said waveguide; at least one ferrite element 5 disposed within said waveguide for providing a closed loop magnetic field therein; a latching conductor longitudinally extending through ferrite element; and a latching control lead connected at each end of said latching conductor wires exiting said waveguide at an angle other than zero degrees relative to each other for minimizing the induced current therein resulting from said radio frequency field.

2. In combination; a waveguide for circularly polarized electromagnetic energy; at least one ferrite element disposed within said waveguide and extending longitudinally therein; a dielectric transformer at each end of said ferrite element for matching the impedance of the empty waveguide to the ferrite loaded guide; a latching conductor extending through said ferrite element and each said dielectric transformer; a latching control wire at each end of said latching conductor; said latching control wires extending through said waveguide at angles other than zero degrees relative to each other for cancelling the induced current in each latching control wire when cross cutting said electromagnetic energy.

3. In combination; a waveguide; means for propagating a circularly polarized electromagnetic wave which may be separated into two orthogonal, linearly polarized TE modes through said waveguide; at least one ferrite element disposed within said waveguide for providing a closed loop magnetic field therein; means extending through said element for switching said element from one remanent state of magnetization to the other remanent state of magnetization; said ferrite element advancing or retarding both i said modes a predetermined number of degrees but the phase quadrature between said modes remaining the same; and latching control wires entering and exiting said waveguide angularly disposed other than zero degrees relative to each other to cancel induced currents therethrough caused by said electromagnetic wave.

The Microwave Journal, April 1965, p. 43. Treuhaft et al., Proc. of the IRE, August 1958,19. 1538.

HERMAN KARL SAALBACH, Primary Examiner.

ELI LIEBERMAN, Examiner.

P. GENSLER, Assistant Examiner. 

